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Making PC Boards 

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Making PC Boards 

Written By: Steven Robert Cypherd 


PCB etching kit (1) 


Making your own printed circuit boards (PCBs) is so easy now. The biggest change is in the 
resist coating on the boards. Now it is less sensitive to ambient light. You do not need a 
safelight or a closed room to work with these new boards. You do have to be careful with 
direct light from any source for more than a minute or so. You do not need a special bulb to 
expose them. Sunlight or a fluorescent light works best. 

Plan your space. I closed my bedroom blinds early in the afternoon and placed the exposer 
frame under my desk. I put a towel over my bathroom window where I have the development 
tray filled and set up. That's it. 

The DATAK Boards use the same developer. They require a Hot 100 - 1 10 degree water 
development and a Cold water rinse to fix the resist. They can be exposed with standard 100 
watt bulb at 12 inches for about 10-15 minutes. 

One thing that is important is that the resist is now sensitive to heat. Any heat. Storing a 
board in its package under direct sunlight will kill your board. Keep them in a cool dark 
place. Heat is a good thing too. When you are done developing your board you just rinse the 
board under warm water and that fixes the resist. Caution here. Once the resist is fixed it is 

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Making PC Boards 

not sensitive to the developer or the light anymore. At this point 91% isopropyl alcohol 
cleans off the resist and you can fix errors or do modifications all in normal light. 

One downside to these single fluorescent tube exposer frames is that the area of good light 
is just three inches wide down the length of the tube. A 4x6 board set at the front of the 
exposer frame will have its back one inch poorly exposed. You must rotate your board. For 
big boards just move them three inches each step through the exposer. Expose for about 6-8 
minutes per step. You can get larger multi-tube exposer frames and special exposer lights. 

Jameco has everything to make a PCB at home: positive resist boards, positive developer, 
etchant, trays and an exposer frame. Look under Electronic Design -^ Prototyping 
Systems. Pre-sensitized boards are available in many standard sizes. The More Products 
category has PCB kits and stuff. I have a single 17" fluorescent tube exposer frame. Mine is 
about 5 V2" high. I got it at Fry's in Burbank, Ca. I also got my Ammonium Persulphate 
etchant at Fry's. Read the instructions that come with the boards. A good exposure makes a 
good PCB. 

I use to design my boards. Fritzing's software lets you export your design to a 
PDF file. Print the PDF file at 100% on clear transparency sheets. For laser printers print on 
the smooth side of the transparency sheet. Cut out the circuit on the board's outline. 

To work with Fritzing you need electronics knowledge and desktop publishing experience. An 
example is the object label used in all views. Right-click the object and select Show Label. 
Select the object and left-click the label and drag it. Right-click the label, select Edit, Size, 
Rotation and Display Details. 

You must get the breadboard and the schematic perfect before you can get a good PCB. No 
"birdcage wires" (Fritzing calls them "rat's nest" wires) anywhere. Test all circuit paths by 
clicking on a node. Then in the PCB remove any rat's nest wires, rotate and move the parts 
and delete and make new circuit paths. You make big changes in the breadboard view first, 
then the schematic view if you need it and then the PCB view. 

In the PCB view deleting a trace is the same as deleting a wire in the breadboard and the 
schematic views. Complete your changes in the PCB and check for rat's nest wires in the 
other views. Make wires out of the correct connections and delete the rest. The default PCB 
is double-sided. Auto-routing is automatic in the other views as you add parts and wires. 
Start moving, orienting and wiring each part on your PCB as you add them. 

To make multiple circuits on one PCB, save your project as somethingAIO. In PCB view 
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Making PC Boards 

click the PCB and in the Parts menu set Sticky to unchecked. Click and drag the PCB away 
from your circuit. Set your PCB to the size that you need. 4x6 is width 101 .6mm and height 
152.4mm. Position your circuit to the left of the PCB and close to where the duplicate will go. 

Drag a selection box around your circuit. Let go. In the edit menu select Duplicate (Ctrl-D). 
Wait for the duplicate circuit to show up. Do not click it. Use the arrow keys to move your 
duplicate onto your PCB. Repeat this for each copy. The breadboard and schematic views 
will be a mess. Line things up nicely. Save your project. Make an editable PDF. Wait for it. 

I do not put Sticky back on. Watch out for Duplicate errors. All of the part labels have copy 
numbers in them. Do not touch the breadboard or the schematic. To fix errors delete the bad 
circuit and make a new duplicate circuit. The more parts in the circuit the longer it will take 
to make a duplicate. 

Step 1 — Making PC Boards 

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• The DATAK Boards require a Hot 100 - 1 10 degree water development and a Cold water 
rinse to fix the resist. 

• Supplies 

© Make Projects 

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Making PC Boards 

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Printed Circuit Boiiid 

Art Work 

• Art Work 

• Exposer 

Step 3 Development 

Pat your et chant into it 3 tray and into a bigger tray with about a half inch 

of hot water in it . E use my 13x9 baking dish. 

Remove the art work from your board 

Place yout board resist side up into the 1 developer 

Start an up counter on your timer 

With fresh developer you should see the art work in two minutes 

Keep agitating the tray 

I rub the board with my gloved lingers. You can use a sponge too 

Wait until all of the copper is shiny, About five minutes 

All of the little holes need to be shiny too 

If it is a double sided board keep flipping it over to check your progress 

It is difficult to over develop your hoard 

The time will increase after each board. The developer gets darker 

If everything is good then rinse your board under warm water. This fixes 

the resist so it is not sensitive to light or the developer anyittore. 
Open the blinds and turn on the lights 
Pour the developer back into its bottle 

st«p * riling »rror« or making modification! 

Using a paper towel wrapped toothpick and 31% Isopropyl Alcohol to clean 
out errors in the resist -Just dampen the corner with the alcohol. You do 
not want to mess up other areas of the resist. 

Add modifications. They have resist pens and art work 

Making Boards 

J fix J 

Fixing Errors 

towel Ik Toothpick 


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Use 91% Isopropyl Alcohol 
lightly dampen paper towel 
orntr. Rub carefully to 

soften resist. Move toothpick 
often to keep resist from getting 
hack on to thebciArd, 
"lean ua/JjH ^H>pper is V 


:he traces * 

Be care with the traces 

am using a Snarpiefl^^crnDi^trati 
and the hoard is already etched. 
The resist is much tougher and takes 
a bit more rubbing. Clean until the 
copper is shiny. 


tenert resist 
with dry paper towel 
Repaired before the 
board was etched 

• Developing 

• Fixing an error 

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Making PC Boards 

Step 5 Etching 

it helps to warm up your ecchant 
Place your board into the etohant copper side up 
Start an up counter on your timer 
Keep agitating the tray 

It it is a double sided board Keep flipping it over to oheck; your progress- 
Change the hot water every fifteen minutes or ao 
It can take an hour or more to etch a board 
Once the etching starts it can move very taetr Check your board every IS 

for the first half hour. Then every ID minutes to the end. 
You can over etch your board 

When you are done etching rinse your board thoroughly 
Pour your etehant back into its Bottle 
Rinse your trays out 
Rinse your tongs and everything else. 

Stepfi Cutting wyour board 

Dreroel circular saws are big enough to keep a straight line easily 
■ aflap*-" 

Dremel has a circular saw i 

found it difficult to u6< 

My fix for Double Sided boards ie using a thin wire like wire wrap wire. Drill 
your boO-eg bigger about -Q19 or big enough to fit your lead easily. Put the 
thin wire into the hole and carefully solder it to the top trace. Try not to 
get udder into the hole. Push a lead through the hole to flatten the wire to 
the sides of the hole. For more current use up to four wires. 

Making Boards 

Double Sided Boards 

I use a small wire like a wire-wrap wire to connect the two sides. Drill your holes 
big enough to fit your lead easily. About .039in. Put the small wire through the 
hole and solder it to the top trace. Do not get too much solder in the hole. 

J Push one of the leads through 
the hole and press the small 
wire to the sides of the hole. 
With square leads you can get 
| about four small wires in. 
Put your lead through the hole 
and bend and trim the small 
wire to fit the bottom trace and 
' solder them. 

Put Clttftll wire 
it the gap 

• Etching 

This document was last generated on 201 2-1 2-1 5 03:50:51 AM. 

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